Within the past year two initially unrelated studies of the uses of outer space have merged. The first, represented by U.S. Pat. No. 3,781,647, involves the collection and transmission to the Earth of solar energy from space. This as an energy program seems to be of marginal economic return (using current or currently projected technology) due to high lift cost if the components of the solar power satellites are shipped up from the Earth. The second began as an academic study of the building of facilities in high Earth orbit which had no clear economic justification. A synthesis of the two concepts was published in Science, Dec. 5, 1976. (Space Colonies and Energy Supply to the Earth: G. K. O'Neill, Vol. 190, page 943. )
The key points are:
a. obtaining materials from the surface of the moon, or other extraterrestrial sources. PA1 b. refining these materials in an industrial plant in a seldom eclipsed high orbit using solar energy. PA1 c. using the materials thus obtained to build solar satellite power plants and additional industrial plant and living spaces. PA1 a. high ratio of output rate to apparatus mass; PA1 b. low input of materials from earth per unit of output; PA1 c. capability of operating in, and if possible making use of the space environment of vacuum, zero gravity, and solar flux. PA1 a. heat a material (not necessarily a metal) to form a vapor; PA1 b. direct the vapor, and PA1 c. deposit the material on a form.
(See also "Future Space Programs 1975", Hearings before the Subcommittee on Space Science and Applications of the Committee on Science and Technology, U.S. House of Representatives, pages 111-188 and "Solar Power from Satellites", Hearings before the Subcommittee an Areospace Technology and National Needs of the Committee on Aeronautical and Space Sciences, U.S. Senate, pages 2-155).
The establishment of industrial facilities in outer space will place unusual requirements upon the apparatus and methods used to process and fabricate materials. Desirable features of apparatus and methods for use in outer space include:
Most metal forming apparatus: for example, rolling mills, punch presses and milling machines, and most metal forming methods, of which stamping, extruding, and machining are examples, are not very productive in terms of the mass of product produced in relation to the equipment mass per unit time. These apparatus and methods tend to require supplies such as dies and cutters which would have to be imported from Earth. They also do not make use of the unique space environment.